A nonlinear multiparameter prestack seismic inversion method based on hybrid optimization approach

Multiparameter prestack seismic inversion is one of the most powerful techniques in quantitatively estimating subsurface petrophysical properties. However, it remains a challenging problem due to the nonlinearity and ill-posedness of the inversion process. Traditional regularization approach can stabilize the solution but at the cost of smoothing valuable geological boundaries. In addition, compared with linearized optimization methods, global optimization techniques can obtain better results regardless of initial models, especially for multiparameter prestack inversion. However, when solving multiparameter prestack inversion problems, the application of standard global optimization algorithms maybe limited due to the issue of high computational cost (e.g., simulating annealing) or premature convergence (e.g., particle swarm optimization). In this paper, we propose a hybrid optimization-based multiparameter prestack inversion method. In this method, we introduce a prior constraint term featured by multiple regularization functions, intended to preserve layered boundaries of geological formations; in particular, to address the problem of premature convergence existing in standard particle swarm optimization algorithm, we propose a hybrid optimization strategy by hybridizing particle swarm optimization and very fast simulating annealing to solve the nonlinear optimization problem. We demonstrate the effectiveness of the proposed inversion method by conducting synthetic test and field data application, both of which show encouraging results.     

A study of the factors influencing the occurrence of landslides in the Wushan area

Due to the complex natural geological conditions, many slope-related geological hazards occur in the Three Gorges Reservoir area in China. This study focuses on the characteristics of landslide development and their underlying mechanisms in this area. A statistical analysis is conducted to determine the characteristics of landslide development in the Wushan area, including the landslide distribution as a function of the elevation, slope, landslide material composition, scale, lithology, boundary conditions, instability mechanism, stratigraphic age, attitude, and sliding direction. The mechanisms of slope instability and the effect on the occurrence of landslides are analyzed. This study provides important reference material for landslide research in the Three Gorges Reservoir area and similar stratigraphic areas.     

Development of efficiently coupled thermo-hydro-mechanical model to predict hydraulic fracture morphology in heavy oil reservoirs

The aim of the study involves examining the effect of heavy oil viscosity on fracture geometry in detail by establishing a heavy oil fracturing model and conventional fracturing model based on thermal–hydraulic–mechanical (THM) coupled theory, Walther viscosity model, and K–D–R temperature model. We consider viscosity and density within the heavy oil fracturing model as functions of pressure and temperature while that as constants within the conventional fracturing model. A heavy oil production well is set as an example to analyze the differences between the two models to account for the thermo-poro-elastic effect. The results show that temperature exhibits the most significant influence on the heavy oil viscosity while the influence of pressure is the least. In addition, a cooling area with a width of 0–1 m and varied length is generated near the fracture. The heavy oil viscosity increases sharply in this area, thereby indicating an area of viscosity increment. The heavy oil viscosity increases faster and is closer to wellbore, and a high viscosity increment reduces the mobility of the heavy oil and prevents the fracturing fluid from entering into the reservoir. The special viscosity distribution results in significant differences in pore pressure, oil saturation, and changing trends between these two models. In the heavy oil reservoir fracturing model, the thermal effect completely exceeds the influence of pore elasticity, and the values of the fracture length, width, and static pressure exceed those calculated in the conventional fracturing model. Thus, a comparison of the measured values indicates that the results obtained by considering viscosity as a function of temperature and pressure are more accurate. Therefore, the results of this study are expected to provide good guidelines for the design of heavy oil fracturing.     

Porosity and wave velocity evolution of granite after high-temperature treatment: a review

The evolution of porosity and changes in wave velocity in granite after high-temperature treatment has been experimentally investigated in different studies. Statistical analysis of the test results shows that there is a temperature threshold value that leads to variations in porosity and wave velocity. At a temperature that is less than 200 °C, the porosity of granite slowly increases with increases in temperature, while the wave velocity decreases. When the temperature is greater than 200 °C (especially between 400 and 600 °C), the porosity quickly increases, while the wave velocity substantially decreases. The temperature ranges of room temperature to 200 and 200–400 °C correspond to the undamaged state and the micro-damage state, respectively. The results confirm that there is an important link between the variations of physical and mechanical properties in response to thermal treatment. By studying the relationships among rock porosity, wave velocity and temperature, this provides the basis for solving multi-variable coupling problems under high temperatures for the thermal exploitation of petroleum and safe disposal of nuclear waste.     

Assessment of water inrush risk using the principal component logistic regression model in the Pandao coal mine,China

In order to improve the accuracy of floor water inrush assessment, the risk prediction model of floor water inrush was established by combining the principal component logistic regression analysis (PCLRA) and GIS spatial geographic analysis. In this paper, the geological data of Pandao coal mine was taken as the engineering background. First of all, main controlling factors of floor water inrush were determined and quantified. Next, PCLRA was used to determine the weight of each factor and establish the mathematical model for predicting the floor water inrush. And then, GIS’s spatial analysis and data processing function was used to draw related single factor thematic maps. Related thematic maps were weighted superposed to draw a floor water inrush zoning map based on PCLRA mathematical model. The study areas were divided into five levels by Jenks optimization method and vulnerability index initial model. And the corresponding threshold range was determined. The results show that (1) the high sensitivity factors in floor failure depth were added to evaluate the water inrush, and the fault fractal dimension was used to replace the fault structure related factors, and the main controlling factors of floor water inrush are more comprehensive; (2) the fitting degree of PCLRA model is high and the test accuracy is 83.3%; (3) the prediction results were well fitted to the actual position of water inrush (three water inrush points are located in the dangerous area, and two water inrush points are located in the relatively dangerous area).     

Middle Jurassic–Early Cretaceous tectonic evolution of the Bayanhushuo area,southern Great Xing’an Range,NE China: constraints from zircon U–Pb geochronological and geochemical data of volcanic and subvolcanic rocks

This study presents new zircon U–Pb geochronology, geochemistry, and zircon Hf isotopic data of volcanic and subvolcanic rocks that crop out in the Bayanhushuo area of the southern Great Xing’an Range (GXR) of NE China. These data provide insights into the tectonic evolution of this area during the late Mesozoic and constrain the evolution of the Mongol–Okhotsk Ocean. Combining these new ages with previously published data suggests that the late Mesozoic volcanism occurred in two distinct episodes: Early–Middle Jurassic (176–173 Ma) and Late Jurassic–Early Cretaceous (151–138 Ma). The Early–Middle Jurassic dacite porphyry belongs to high-K calc-alkaline series, showing the features of I-type igneous rock. This unit has zircon ε_Hf(t) values from +4.06 to +11.62 that yield two-stage model ages (T_DM2) from 959 to 481 Ma. The geochemistry of the dacite porphyry is indicative of formation in a volcanic arc tectonic setting, and it is derived from a primary magma generated by the partial melting of juvenile mafic crustal material. The Late Jurassic–Early Cretaceous volcanic rocks belong to high-K calc-alkaline or shoshonite series and have A₂-type affinities. These volcanics have ε_Hf(t) and T_DM2 values from +5.00 to +8.93 and from 879 to 627 Ma, respectively. The geochemistry of these Late Jurassic–Early Cretaceous volcanic rocks is indicative of formation in a post-collisional extensional environment, and they formed from primary magmas generated by the partial melting of juvenile mafic lower crust. The discovery of late Mesozoic volcanic and subvolcanic rocks within the southern GXR indicates that this region was in volcanic arc and extensional tectonic settings during the Early–Middle Jurassic and the Late Jurassic–Early Cretaceous, respectively. This indicates that the Mongol–Okhotsk oceanic plate was undergoing subduction during the Early–Middle Jurassic, and this ocean adjacent to the GXR may have closed by the Late Middle Jurassic–Early Late Jurassic.     

准噶尔盆地东北部侏罗系砂岩型铀矿成矿环境与找矿方向探讨

文章从蚀源区铀源条件、中新生代构造演化条件、侏罗系沉积建造特征及后生蚀变特征等角度分析了准噶尔盆地东北部砂岩型铀矿的区域成矿条件,认为卡拉麦里山的富铀花岗岩体为该区砂岩型铀成矿提供了丰富的铀源,中侏罗统含煤碎屑岩建造为砂岩型铀成矿提供了良好的容矿空间,侏罗纪以来多期次不整合面的发育为含铀含氧水的渗入改造提供了通道及时间,为大规模层间氧化带的发育提供了物质基础。研究结果显示,卡拉麦里山北坡为最有利的砂岩型铀矿找矿部位,其主要找矿目标层位为中侏罗统头屯河组,找矿类型为层间氧化带型。     

Club convergence and spatial distribution dynamics of carbon intensity in China’s construction industry

Climate change caused by carbon emissions continuously threatens sustainable development. Due to China’s immense territory, there are remarkable regional differences in carbon emissions. The construction industry, which has strong internal industrial differences, further leads to carbon emission disparity in China. Policymakers should consider spatial effects and attempt to eliminate carbon emission inequality to promote the sustainable development of the construction industry and realize emission reduction targets. Based on the classic Markov chain and spatial Markov chain, this paper investigates the club convergence and spatial distribution dynamics of China’s carbon intensity in the construction industry from 2005 to 2014. The results show that the provincial carbon intensity in the construction industry is characterized by “convergence clubs” during the research period, and very low-level and very high-level convergence clubs have strong stability. Moreover, the carbon intensity class transitions of provinces tend to be consistent with that of their neighbors. Furthermore, the transition of carbon intensity types is highly influenced by their regional backgrounds. The provinces with high carbon emissions have a negative influence on their neighbors, whereas the provinces with low carbon emissions have a positive influence. These analyses provide a spatial interpretation to the “club convergence” of carbon intensity.     

Application on Floor Water Inrush Evaluation Based on AHP Variation Coefficient Method with GIS

The prediction and prevention of floor water inrush is directly related to the safety of the coal mine production. The previous evaluation method of floor water inrush was more one-sided and lacked main control factors related to mining conditions. In order to evaluate the floor water inrush more accurately, under the project background of geological data of Wanglou coal mine, stope width, mining depth, fault scale index, water pressure, water abundance and thickness of aquifer were selected as main controlling factors of floor water inrush. Combined with the subjective weight analytical hierarchy process and the objective weight variation coefficient method, the weight coefficients corresponding to the main controlling factors were obtained respectively. The thematic map of the risk assessment of coal seam floor water inrush was drawn by combining the constructed comprehensive weight vulnerability index model and geographic information system. The results show that: ① according to the actual geological data of mine, two fault related factors were removed. And stope width and mining depth were increased as the main controlling factors to evaluate floor water inrush. It is easier to compare and calculate the weight of evaluation factors. ② The constructed comprehensive weight vulnerability index model can comprehensively evaluate the risk of floor water inrush. And the results of the evaluation are more accurate. ③ The related thematic maps can directly reflect the risk of floor water inrush, which is of guiding significance for the prediction and prevention of coal seam floor water inrush.     

华北地台北缘集宁地区古元古代片麻状石榴花岗岩的深熔成因及地质意义

本文对华北克拉通北缘集宁地区空间上密切共生的片麻状石榴花岗岩和孔兹岩系富铝片麻岩的岩相学、地球化学及年代学特征进行了对比研究。SHRIMP锆石U-Pb定年方面,在富铝片麻岩中获得了1910±10Ma和1839±13Ma变质锆石年龄,在片麻状石榴花岗岩中获得了1919±17Ma的变质重结晶锆石年龄。在石榴花岗岩的石榴石包裹体中识别出与富铝片麻岩相对应的进变质阶段(M1)和峰期阶段(M2)的矿物组合,由此确认富铝片麻岩的变质作用和导致石榴花岗岩形成的深熔作用是同一构造热事件的产物。通过对二者变质作用演化及特征变质矿物的对比,认为深熔作用主要发生在峰期后等温降压阶段(M3),石榴花岗岩中的石榴石为深熔作用过程中的残留矿物相或转熔矿物相,而石榴花岗岩则是混合有大量残留矿物相的熔体结晶的产物。对片麻状石榴花岗岩和富铝片麻岩的地球化学组成特征进行了对比分析,片麻状石榴花岗岩既有一定的继承性,又有十分明显的变异性。变异性表现为:1)石榴花岗岩主量和微量元素含量分布极不均匀,微量元素含量普遍低于源岩(Cs、Rb、Th、U、Nb、Ta、Zr、Hf等);2)大离子亲石元素Cs和生热元素U、Th亏损明显,Sr相对富集;3)高场强元素Nb、Ta、P、Ti的明显亏损;4)铕异常变化大,存在铕富集型、铕平坦型和铕亏损型共存的稀土配分曲线的岩石,这是深熔成因石榴花岗岩最突出的表现,也可能是原地-半原地深熔花岗岩的主要地球化学标志。综合区域上的地质资料,认为深熔作用与碰撞后伸展构造背景下基性岩浆底侵事件有关。